The prostaglandins are members of a family of hormonal substances which have very potent physiological effects. Among these effects, the abortifacient, antihypertensive and bronchodilating properties are the most widely investigated; but other important biological actions have been evidenced by several authors. See, for instance, the review by M. P. L. Caton in "progress in Medicinal Chemistry" Volume 6, part 2, page 317, edited by G. Ellis and G. B. West, Butterworth & Co., London 1971. The prostaglandins are optically active derivatives of prostanoic acid, i.e., a substituted cyclopentane compound having the following structure: ##STR1## Although they are naturally occurring in a number of tissues, many chemical approaches to their synthesis have been reported in the literature as their concentration in said tissues is very low.
One of the most convenient approaches to the total chemical synthesis of prostaglandins is reported by E. J. Corey and coworkers, J. Am. Chem. Soc., 91, 5675 (1969). This approach requires the synthesis of suitable precursors which are derivatives of the lactone of 2-hydroxy-1-cyclopentaneacetic acid. The synthetic pathway reported by E. J. Corey and coworkers in J.A.C.S. 92, 397, 1970 for optically-active prostaglandins as the naturally occurring forms, requires resolution of an intermediate (+)-cyclopentenehydroxy acid by means of (+)-ephedrine salts to obtain the (-)-isomer. The latter is then transformed into the lactone, which is the key compound for a synthetic stereo-controlled route to prostaglandins in the F and E series, i.e., those having oxy functions at positions 9 and 11. Prostaglandins E may be further transformed into prostaglandins A according to literature methods.